Motion and footpoint brightening in an M flare, 20-jan-99

Science Nugget: Jan 22, 1999

The graph above shows that there was a tremendous flare late in the day on 20-jan-99. The X-ray flux reached M5.2 on the GOES scale, and a coronal mass ejection (CME) was observed by the Mauna Loa Solar Observatory. SXT was in daylight when the flare occurred, and made some great images. The analysis is underway, but we present here a preliminary look at some of the motion and brightening that occurred.

A brightening arcade:
The event took place on the northeast limb, and manifested itself as a large arcade. The SXT flare mode was actually triggered before the arcade reached its maximum brightness; as a result we have a sequence of images that shows the brightening as it occurs. Two movies are linked below:

GIF movie, 645 kbytes

MPEG movie, 75 kbytes

Footpoint motion:
As the event unfolded, the footpoints of the arcade were seen to brighten. An interesting phenomenon is that the brightening appeared to move, as subsequent magnetic field lines were perturbed. The appearance of the moving brightness is reminiscent of the Northern Lights! Two movies are linked below:

GIF movie, 980 kbytes

MPEG movie, 118 kbytes

The bright knot at the north end of the row of footpoints shows the most noticeable motion; HXT saw a bright source at that same location.

More to come?
There are other motions visible in the loops that make up the arcade, and in the loops that stretch over its top. We will take a closer look at these, and hope to present them in a future Weekly Science Nugget. Stay Tuned!

Jan. 23, 1999: David McKenzie (email mckenzie@isass0.solar.isas.ac.jp)